Method of bleaching hair or wool

ABSTRACT

Bleaching of hair or wool with alkaline peroxide solutions is accelerated and incidental decomposition of keratin is lessened by first impregnating the hair or wool with an aqueous solution of ferrous salt and chelating agent having log KMA from two to eight.

United States Patent 1 1 3,632,295

[72] Inventors Kathleen Ella]! Reiel'encescfled Silver Spring; UNITED STATES PATENTS LeslekJ-w'tlfmmmckvillebmmmd- 2,149,319 3/1939 Soussa 8/l02X 1 A PP1-N- 820,307 2,875,018 4/1959 Eastonetal.... 8/lll 1 Filed APP-29,1969 2,914,374 11/1959 Harrisetal..... 8/111 1 Patented Jan-4,1972 3,l93,464 7/1965 Edmanetal. s/111x 1 Asslsnee Thecillettecmpany 3,373,444 4/1968 Swanson 8/lll x Boston, Mass.

Primary Examiner-Mayer Weinblatt Attorney-R. W. Furlong [54] METHOD OF BLEACHING HAIR 0R WOOL 7 Claims, No Drawings [52] U.S.C| 8/111,

ABSTRACT: Bleaching of hair or wool with alkaline peroxide solutions is accelerated and incidental decomposition of 8/l0. l 8/l0.2, 8/ 102, 252/ l 86, 424/62, 424/7 keratin is lessened by first impregnating the hair or wool with [5 l Int. Cl D06| 3/02 [50] Field ofSeareh 8/111, 102, 10.1, 10.2; 252/186; 424/62, 70

an aqueous solution of ferrous salt and chelating agent having log K from two to eight.

METHOD OF BLEACHING HAIR R WOOL This invention relates to the bleaching of keratinous fibers such as human hair or animal hair e.g., wool and to a composition for use in such bleaching and pertains more specifically to a two-stage process in which the fibers are first impregnated with an aqueous solution of ferrous salt and chelating agent, then with an aqueous alkaline solution of hydrogen peroxide.

It has previously been proposed to bleach hair by first impregnating it with an aqueous solution of ferrous ion and subsequently to treat it with an aqueous alkaline solution of hydrogen peroxide, the ferrous ion acting as a catalyst to accelerate the bleaching process. However, this procedure suffers from the disadvantage that a long time is required for the impregnation step and further that the ferrous ion tends to become associated with the keratin of the fiber as well as with the melanin coloring agent present in the fiber, leading to destruction of the keratin and consequent weakening of the fiber in addition to the desired decolorization. It has also been proposed to impregnate the fibers with an aqueous solution of ferrous salt, then leach the impregnated fiber with acid before the bleaching step in order to remove the ferrous ion from the keratin while leaving it with the coloring agent, but this additional step is expensive and time consuming.

It has now been found that by impregnating keratinous fibers with an aqueous solution containing in addition to ferrous salt a chelating agent having a chelate formation constant (K with ferrous ion such that log K is from 2 to 8, the time required for the impregnation step is greatly reduced and simultaneously the injurious effects of the subsequent bleaching process on the keratin of the fibers is minimized. The chelate formation constant referred to herein, K is the one determined at an ionic strength of 0.1 and at pH 5, as well known in the art. See for example, Chaberek et al., Organic Sequestering Agents, New York (1959).

The concentration of ferrous salt, i.e., of ferrous ion, in the aqueous impregnating medium or solution may vary from 0.05 to 0.15 molar. If the concentration of ferrous salt is less than 0.05 molar, the time required for impregnation of the hair becomes undesirably long, even at elevated temperature, while increasing the concentration above 0.15 molar has no effect upon the process. Any of a wide variety of water-soluble ferrous salts may be employed as the source of ferrous ion, such as the fonnate, acetate, bromide, chloride, iodide, nitrate, sulfate, lactate, tartrate, and the like. Included among the chelating agents which may be employed are for example ascorbic acid, citric acid, serine, and ethylene diamine. The molar concentration of chelating agent present in the impregnating medium should be from 0.2 to 5 times the molar concentration of the ferrous salt. It is desirable, but not essential, to include in the solution in addition a small amount of reducing agent which is inert to, i.e., which does not precipitate the ferrous ion nor form a complex with it. The chelating agents themselves may in some cases be termed reducing agents. These additional reducing agents inert to the ferrous ion include materials such as an alkali metal (e.g., sodium) formaldehyde sulfoxylate, alkali metal sulfites or alkali metal thiosulfates, and are desirably present particularly when serine is used as the chelating agent, in order to prevent the formation of ferric hydroxide precipitate in the solution during treatment of the hair. The concentration of such reducing agent may be from 0.005 to 0.05 molar.

It is advantageous to include a buffer system in the solution to maintain the acidity within the desired range and also to maintain the total ionic strength above the minimum desired level. The buffer should, of course, be one which does not precipitate the ferrous salt nor form a complex with it. For best results a buffer mixture of sodium acetate and acetic acid in the molar proportion of :3, providing a pH of about 5, is used; other buffer systems may be used, such as a mixture of potassium acid phthalate with sodium hydroxide in the molar proportion of 5 :4.

For best results the total ionic strength of the impregnating solution should be from 0.5 to 2.5, optimum results being achieved at a value of about 2.0, and the pH should be from 3.5 to 6.

The temperature of the solution may vary from room temperature (20 C.) to as high as the boiling point, although when'hair is treated on the head, the maximum temperature which can comfortably be used is about 55 C. unless special equipment and techniques are employed.

The time required for diffusion of the ferrous ion from the solution into the keratinous fiber may be as little as minutes at room temperature in order to obtain an appreciable accelera tion of the subsequent bleaching step by the ferrous ion catalyst, but best results are usually obtained by maintaining contact of the hair fibers with the solution of ferrous salt for 0.5 to 1.5 hour at a temperature from 35 to 60 C., much less than the 3m 4 hours required when using a solution of ferrous salt without chelating agent.

Following impregnation of the keratinous fibers with the aqueous solution of ferrous salt and chelating agent, it is advantageous, but not essential, to rinse the fibers with water to remove ferrous ion which is not bonded to the melanin and which therefore is of no value in catalyzing the subsequent decomposition of the coloring agent and which serves to accelerate wasteful and ineffective decomposition of the peroxide in the subsequent bleaching step. Such loss of peroxide is noticeable particularly when log K of the solution is near the lower end of the permissible range, making a rinse step particularly desirable under these conditions.

The subsequent bleaching step is conventional aqueous alkaline peroxide bleaching process in which the fibers are maintained in contact with an aqueous solution containing 1-6 percent peroxide (measured as hydrogen peroxide) adjusted to pH 8-11 with any suitable base such as an alkali metal hydroxide, but preferably ammonium hydroxide at a temperature from room temperature to 60 C.

The effectiveness of the process in removing color from hair can be measured by comparing it with the decolorization produced by a conventional single-stage bleach process using 3 percent aqueous hydrogen peroxide solution at 35 C. adjusted to pH 10 with ammonium hydroxide for various time periods. The extent of decomposition of the keratin in the fiber by the peroxide can be measured by measuring the extent to which the fiber retains water using a standard procedure involving reduction with thioglycolatc and neutralization with peroxide, immersion in water buffered at pH 7, and centrifugation, the greater retention indicating greater decomposition.

From these tests it appears that fibers pretreated with ferrous salt and chelate in accordance with the present invention can be bleached i.e., decolorized by a 30-minute bleach to the same extent as other fibers, having no pretreatment, are bleached in 2 to 2.5 hours, and with substantially less decomposition of keratin.

The following specific examples are intended to illustrate more clearly the nature of the present invention without acting as a limitation upon it.

EXAMPLE 1 One gram of dark brown Caucasian hair was immersed for 1 hour at 55 C. in 25 ml. of solution consisting of:

0.98 g. ferrous ammonium sulfate hexahydrate 0.44 g. ascorbic acid 15 ml. 2 molar sodium acetate buffer*( *The sodium acetate buffer was prepared by mixing 1 liter of 2 molar aqueous sodium acetate with 300 ml. of 2 molar aqueous acetic acid.) 10 ml. water The pH of the above solution remained at a value of 5 during treatment of the hair, and the total ionic strength was 1.9.

The hair was removed from the solution after 1 hour and thoroughly rinsed with tapwater. Bleaching of the hair was then accomplished by immersing it in 20 ml. of aqueous 0.5 molar ammonium hydroxide containing 3 percent by weight of EXAMPLE 2 One gram of black Oriental human hair was immersed for 1 hour at 55 C. in 25 ml. of solution consisting of:

0.98 g. ferrous ammonium sulfate hexahydrate 0.44 g. ascorbic acid 15 ml. 2 molar sodium acetate buffer as in example l 10 ml. water The pH of the solution remained at throughout the immersion and was 5, the total ionic strength was 1.9. The hair was then rinsed well with tapwater, and finally bleached as described in example 1.

Following the bleach period of 30 minutes, the pretreated Oriental hair had bleached to a blond shade. A bleaching time of 2 hours was required in order to obtain an equivalent degree of bleaching of Oriental hair having no pretreatment. The water retention value of the latter was 96 percent by weight as compared to 72 percent for the former.

EXAMPLE 3 One gram of dark brown Caucasian hair was immersed for 1 hour at 55 C. in 25 ml. of solution consisting of:

0.49 g. ferrous ammonium sulfate hexahydrate 0.52 g. citric acid monohydrate 20 ml. 2 molar sodium acetate buffer as in example 1 5 ml. water The pH of the solution was 4.7 throughout immersion of the hair and the total ionic strength was 2.0. The hair was removed from the solution and rinsed well with tapwater, then bleached as described in example 1. After 30 minutes, the extent of bleach obtained was equivalent to that obtained after 45 minutes bleach, under the same conditions, of hair having no pretreatment, and the water retention value of the latter was 105 percent by weight as compared to 75 percent for the former.

EXAMPLE 4 One gram of dark brown Caucasian hair was immersed for 1 hour at 55 C. in 25 ml. of solution consisting of:

0.49 g. ferrous ammonium sulfate hexahydrate 0.26 g. serine 004 g. sodium formaldehyde sulfoxylate 15 ml. of 2 molar sodium acetate buffer as in example 1 ml. water The pH of the solution remained at 5.1 throughout the treatment of the hair and the total ionic strength was 1.6. The addition of the reducing agent, sodium formaldehyde sulfoxylate prevented the formation of ferric hydroxide precipitate.

The hair was rinsed well with tapwater, followed by bleaching as described in example 1. After bleaching for 30 minutes, the fibers were light blond in color, equivalent to a bleach level attained by hair which had no pretreatment after a 2-hour immersion in bleach under the same conditions. The latter hair exhibited a water retention of percent by weight, while the former exhibited only 77 percent.

EXAMPLE 5 One gram of black Oriental hair was immersed for 1 hour at 50 C. in 25 ml. of solution consisting of:

0.49 g. ferrous ammonium sulfate hexahydrate 0.10 g. ethylene diamine 0.22 g. acetic acid (glacial) 25 ml. water The pH of the solution was initially 5.2, but it dropped to 5.0 during the course of the immersion and the total ionic strength of the solution was 0.5. The hair was then thoroughly rinsed in water and subjected to the bleaching procedure as described in example 1 for 30 minutes, after which time it had been bleached to the same extent as hair, not subjected to the pretreatment, exhibited after 1.5 hour of bleaching under the same conditions, and also exhibited less water retention than the latter.

Similar results are obtained by treating wool and other animal hair by the procedures of the foregoing examples.

What is claimed is:

1. In the method of bleaching human hair by contacting it with an aqueous hydrogen peroxide solution at pH 8-1 1, the step which comprises first impregnating the hair with an aq ueous solution containing 0.05 to 0.15 molar dissolved ferrous salt and a dissolved organic chelating agent in a concentration from 0.2 to 5 times the molar concentration of the salt at a temperature from room temperature to the boiling point, said chelating agent having a chelate formation constant with ferrous ion such that log K is from 2 to 8, the total ionic strength of the ferrous salt solution being from 0.5 to 2.5.

2. The method as claimed in claim 1 in which the total ionic strength of the ferrous salt solution is from 2.0 to 2.5 and the solution in addition contains a buffer to provide a pH from 3.5 to 6.

3. The method as claimed in claim 1 in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is ascorbic acid.

4. The method as claimed in claim 1 in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is citric acid.

5. The method as claimed in claim I in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is ethylene diamine.

6. The method as claimed in claim 2 in which the ferrous salt solution in addition contains a reducing agent which is a member of the class consisting of alkali metal fonnaldehyde sulfoxylates, alkali metal sulfites, and alkali metal thiosulfates.

7. The method as claimed in claim 6 in which the chelating agent is serine. 

2. The method as claimed in claim 1 in which the total ionic strength of the ferrous salt solution is from 2.0 to 2.5 and the solution in addition contains a buffer to provide a pH from 3.5 to
 6. 3. The method as claimed in claim 1 in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is ascorbic acid.
 4. The method as claimed in claim 1 in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is citric acid.
 5. The method as claimed in claim 1 in which the ferrous salt solution in addition contains a buffer to provide a pH from 3.5 to 6 and the chelating agent is ethylene diamine.
 6. The method as claimed in claim 2 in which the ferrous salt solution in addition contains a reducing agent which is a member of the class consisting of alkali metal formaldehyde sulfoxylates, alkali metal sulfites, and alkali metal thiosulfates.
 7. The method as claimed in claim 6 in which the chelating agent is serine. 